In the satellite communications and telemetry field it is desirable to have tracking antennas that are inexpensive to construct and that are virtually maintenance free. To permit changes in its orientation, an antenna reflector must be able to pivot about one or more axes, depending on the type of mounting used.
One type of mounting structure is the elevation over azimuth type in which structures must provided for independent rotation about the horizontal or elevation axis and also about the vertical or azimuth axis. Previous structures have utilized different drive assemblies to provide the rotational power to achieve the proper elevation and azimuth orientations. Such drive assemblies are more expensive to design, manufacture and maintain. Therefore, there has existed a need for a modular drive assembly that can be used in either the elevation or azimuth orientation.
Typical drive assemblies are gear driven. The metal-to-metal contact of gear teeth requires lubrication around the area of the teeth. In some types of gear housing, such as helicopter gear boxes, the lubricant occupies a considerable volume of space within the housing, yet is needed only in the area of the gear teeth and related bearings. The excess lubricant adds weight to the assembly and requires more lubricant than necessary to properly operate the assembly. The problem of excess lubricant has been partially solved by the use of inserts placed within the gear housing. The insert occupies space otherwise occupies by the lubricant, and is usually lightweight and inexpensive. Minimizing the clearance around the gear meshes and bearing surface maintains lubricant contact with the surfaces needing lubrication.
There are, however, problems remain with existing inserts. First, the insert material eventually tends to absorb the lubricant, thus, defeating the purpose for having an insert by increasing lubricant usage and increasing the weight of the insert. Second, some gear assemblies may be comprised of optional, interchangeable pieces of equipment which occupy space within the gear housing only when present. For exaple, a drive assembly may be designed to house two motor units and two data packages that are easily removeable when not in use. Inserts that have open areas to accommodate unused optional equipment require more lubricant to fill the open areas. Therefore, a need exists for a system capable of accommodating optional equipment which extends into the gear housing without significantly increasing the open space within the housing filled by lubricant.